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Clinical Rehabilitation 2009; 23: 1086–1092
The effect of eating utensil weight on functional
arm movement in people with Parkinson’s
disease: a controlled clinical trial
Hui-Ing Ma Department of Occupational Therapy and Institute of Allied Health Sciences, Wen-Juh Hwang Department of
Neurology, Pei-Luen Tsai and Yung-Wen Hsu Department of Occupational Therapy, College of Medicine, National Cheng
Kung University, Tainan, Taiwan
Received 10th November 2008; returned for revisions 21st March 2009; revised manuscript accepted 13th June 2009.
Objective: To investigate the effect of eating utensil weight on kinematic
performance in people with Parkinson’s disease.
Design: A counterbalanced repeated-measures design.
Setting: A motor control laboratory in a university setting.
Subjects: Eighteen adults with Parkinson’s disease and 18 age-matched controls.
Experimental conditions: Each participant performed a food transfer task using
spoons of three different weights: lightweight (35 g), control (85 g) and weighted
(135 g). Kinematic variables of arm movement were derived and compared
between conditions.
Main measures: Kinematic variables of arm movement, including movement time,
peak velocity and number of movement units.
Results: Utensil weights significantly affected the movement kinematics
of all participants. Both groups had fewer movement units in the lightweight
condition (Parkinson’s disease group: 22.18, controls: 19.89) than in the
weighted condition (Parkinson’s disease group: 22.68, controls: 21.36),
suggesting smoother movement in the former condition. In addition, both
groups had higher peak velocity in the lightweight than in the weighted condition.
Conclusions: Our findings suggest that a lightweight utensil may facilitate
smoother and higher-velocity arm movement than a weighted one in people with
Parkinson’s disease.
Introduction
People with Parkinson’s disease have motor
problems of tremor, rigidity and bradykinesia.
1
Many of them report difficulties manipulating
feeding utensils.
2
According to dynamic systems
theory, movement patterns are influenced by task
constraints (e.g. weight of utensils) and personal
characteristics (e.g. neurophysiological factors).
3,4
Some rehabilitation therapy textbooks
5,6
recom-
mend weighted utensils to reduce tremor and to
facilitate the manipulation of utensils. Weighted
utensils are commercially available for this
purpose.
Although recommending weighted utensils is a
long-established practice, few studies
7–9
have
Address for correspondence: Hui-Ing Ma, Department of
Occupational Therapy and Institute of Allied Health
Sciences, College of Medicine, National Cheng Kung
University, 1 Ta-Hsueh Road, Tainan 701, Taiwan.
e-mail: huingma@mail.ncku.edu.tw
ßThe Author(s), 2009.
Reprints and permissions: http://www.sagepub.co.uk/journalsPermissions.nav 10.1177/0269215509342334
investigated the efficacy of the recommendation
for people with tremor. The results of these studies
indicate that weighting may be beneficial for
people with cerebellar tremor or may change the
frequency of physiological tremor. However, they
do not show that any benefits accrue to people
with Parkinson’s disease or that weighting affects
the tremor associated with Parkinson’s disease.
A recent examination of the effects of weights
measured the amplitude and frequency of tremor
while participants with Parkinson’s disease were
holding a built-up spoon (108 g), a weighted
spoon (248 g) and a built-up spoon and a weighted
wrist cuff (470 g).
8
Consistent with previous
reports,
7–9
there were no significant differences
across conditions in any measure of tremor ampli-
tude or frequency.
10
This suggests that there is no
support for the clinical recommendation of using
weighted utensils to alleviate postural hand tremor
in Parkinson’s disease.
Another line of studies that examined the
control of grasping force in Parkinson’s dis-
ease
11–13
may also provide insight into the poten-
tial influence of weights. People with Parkinson’s
disease were asked to grasp and lift an object
of which the weight and centre of mass were chan-
ged from trial to trial. The participants showed
inaccurate scaling of fingertip force amplitude
before object lift and later implementation of
appropriate force amplitude among the digits
during the lift.
11
The results suggest impaired
coordination of multi-digit grasping forces
during object grasping and lifting. Accordingly,
weighted utensils may put people with
Parkinson’s disease at a disadvantage by compli-
cating the coordination required to hold and
manipulate a weighted utensil.
We examined the effect of weights on movement
kinematics in Parkinson’s disease. In view of
the reported impaired control of grasping force,
to have a full spectrum of weight effects,
we tested not only weighted and unweighted uten-
sils, but also a lightweight one. In addition, we
focused on kinematic analysis of movement
during a functional food transfer task, rather
than on the amplitude and frequency of tremor,
to understand the movement quality and motor
control strategies when using utensils of different
weights.
Methods
We enrolled a sample of convenience composed of
18 participants with Parkinson’s disease and 18
age-matched healthy controls. The University
Hospital Institutional Review Board approved
this study, and all participants signed the informed
consent before the experiment began. To be
included, participants had to meet the following
criteria: (1) diagnosed with idiopathic
Parkinson’s disease, (2) stable medication usage,
(3) between 40 and 75 years old, (4) normal or
corrected-to-normal vision and hearing, (5) neither
a history of neurological conditions other than
Parkinson’s disease nor any musculoskeletal dis-
orders affecting arm movement, and (6) able to
follow experimental instructions. The inclusion
criteria for the age-matched controls were identical
to criteria 3–6 above.
Design and procedures
We used a counterbalanced repeated-measures
design.
14
Each participant performed the experi-
mental task using spoons of three different
weights: (A) lightweight: 35 g, (B) control: 85 g,
and (C) weighted: 135 g. Each participant was ran-
domly assigned to one of three experimental
sequences (ABC, BCA and CAB) by means of
sealed envelopes.
When the participant arrived at the motion ana-
lysis lab, first, the maximum grip strength of the
participant’s dominant hand was measured using
the standardized procedure; the average of three
trials was recorded. Next, the participant was
asked to sit at a table and adjust their seat to a
comfortable distance from the table. A small,
empty bowl and a big soup bowl filled with
water were placed in front of the participant,
with the small bowl closer to the participant’s
body. The experimental task required the partici-
pant to reach with the spoon for the water in the
big bowl, scoop up the water, and transport it
back and into the small bowl. We controlled the
distance between the small and big bowls by mark-
ing the table and placing the bowls on the same
markings for each test.
For each condition, the participants performed,
at their own pace, three successive scoops for
Effect of utensil weight in Parkinson’s disease 1087
practice, and then, after a short break, the partic-
ipant performed 10 successive scoops for the test.
Only the test trial was used for kinematic analysis.
The instruction was to ‘Do the task as you would
normally do it and don’t spill out the water.’ If
water spilt from the spoon, the trial was discarded
and then redone. All participants did the task suc-
cessfully without apparent tremor hindering their
performance.
Materials
A big soup bowl (17.5 cm in diameter, 5.5 cm
high) and a small bowl (10.5 cm in diameter,
5.2 cm high) were used. A spoon was designed
with a plastic tube-shaped handle, into which stan-
dard weights could be placed. The handle was
10.2 cm long with a diameter ranging between
2.5 cm at the end and 1.9 cm where spoon was
attached. The handle was cone-shaped to fit com-
fortably in the hand. A survey of utensils on the
market revealed that a lightweight spoon weighed
between 30 g and 45 g. Therefore, we made our
lightweight spoon 35 g, our control spoon 85 g,
and our weighted spoon 135 g.
Measures
We measured each participant’s grip strength
using a hand dynamometer (Jamar; FEI,
Irvington, NY, USA). In addition, a three-dimen-
sional ultrasonic measuring system (CMS-HS;
Zebris Medical GmbH, Isny, Germany) was used
to collect movement kinematics. The CMS-HS uses
microphone markers that receive ultrasonic signals
from a fixed set of transmitters in a measuring unit.
One marker was attached to the radial styloid of the
participant’s dominant hand to record arm move-
ment. The position of the marker over time was
sampled by the system at a frequency of 50 Hz; spa-
tial resolution was 0.085 mm. After being collected,
the data were stored for off-line analysis. The three-
dimensional position data were filtered using a
non-parametric regression method with kernel esti-
mates of order (vþ4).
15
The bandwidths for data
smoothing were 50 ms for the position signal and
70 ms for the velocity signal.
16
The following kinematic variables were included
as dependent variables: movement time, amplitude
of peak velocity, percentage of movement time for
acceleration phase and number of movement
units. Movement time is the length of time it
took to execute the movement: the faster the
movement, the shorter the movement time. Peak
velocity is the highest instantaneous velocity
during the movement. The amplitude of peak
velocity is correlated with the functional efficacy
of a motor system
17
and the force of a move-
ment.
18,19
The higher the peak velocity, the more
forceful the movement and the less the unneces-
sary premovement co-contraction.
In addition, when the hand reaches for a target,
it generally accelerates first toward the target and
then decelerates to change the direction or correct
the trajectory.
20
The percentage of movement time
for acceleration phase reflects the time used to
accumulate the impulse for movement relative to
the whole movement time. Finally, a movement
unit consists of one acceleration phase and one
deceleration phase.
21
A smooth movement would
have only one change in the direction of the forces
and, therefore, only one movement unit.
For each trial, movement was dissected into
‘reach’ and ‘return’ segments because of the oppo-
site directions involved in these two segments.
Kinematic scores for peak velocity and percentage
of movement time for acceleration phase were sep-
arately derived for each segment. For movement
time and number of movement units, because their
quantity can be added, their kinematic scores were
the sum of scores in reach and return segments.
Statistical analysis
Three (weight condition: lightweight vs. control
vs. weighted) 2 (group: Parkinson’s disease vs.
control) mixed analyses of variance (ANOVAs)
were computed on the kinematic scores.
Omnibus F-values derived from the 3 2 mixed
ANOVAs indicated whether there were any statis-
tically significant differences between the three
conditions (non-directional).
To understand the trend of performance, con-
trast weights (:1, 0, þ1) of linear trend were
assigned to the conditions to derive a focused F.
22
Focused Fwas further used to calculate the effect
size r. Effect size indicates the magnitude of the
effect and is free from sample size influence.
1088 Hui-Ing Ma et al.
According to Cohen,
23
an rof 0.10 indicates a
small effect, of 0.30, a moderate effect, and of
0.50, a large effect. Commercial statistical software
(SPSS version 13.0; SPSS Inc., Chicago, IL, USA)
was used to analyse the data.
Results
Table 1 shows the characteristics of study partici-
pants. There was no significant difference between
the Parkinson’s disease and control groups in age
(t¼0.98, P¼0.33) or grip strength (t¼0.53,
P¼0.60). Most of our participants were at mod-
ified Hoehn and Yahr stage
24
2, meaning that their
symptoms were bilateral and they had minimal
disability. In addition, evaluation by the Unified
Parkinson’s Disease Rating Scale
25
indicated that
most participants with Parkinson’s disease were
somewhat slow and clumsy when using utensils,
and most had slight resting tremor, postural
tremor and rigidity in their dominant hand. With
respect to bradykinesia, the participants had some
mild slowing or reduced amplitude, or both, in
their dominant hand movement. One of the 18
participants was left-handed and was matched to
a control with the same dominant hand.
The results of mixed ANOVA indicated that the
group-by-condition interaction effect was not sig-
nificant for any of the dependent variables. For
the effect of spoon weight, we found significant
results for peak velocity, percentage of movement
time for acceleration phase and number of move-
ment units (Table 2). Peak velocity was lower
when the Parkinson’s disease group and control-
group participants used a heavier spoon for the
reach (focused F(1,34) ¼6.82) and return
(F¼4.37) segments. The participants also spent a
higher percentage of movement time accelerating
when using a heavier spoon to reach for the soup
in the big bowl (F¼7.37). In addition, the partici-
pants showed more movement units with a heavier
spoon (F¼4.35). The effect was moderate for
these significant variables. For the other variables,
the effect of spoon weight was small and non-sig-
nificant. Finally, regarding the group difference,
peak velocity was significantly lower in the
Parkinson’s disease than in the control groups
(reach: F¼9.62, return: F¼5.85).
Discussion
We showed that the movement kinematics of
people with Parkinson’s disease and controls
was affected by the weight of a utensil.
Table 1 Characteristics of study participants
Groups PD (n¼18) Controls (n¼18)
Sex, female/male 4/14 5/13
Age, mean SD, years 66.3 9.3 63.3 9.0
Grip strength, mean SD, kg 28.68 8.28 30.2 8.76
Duration of PD, mean SD, years 4 4.1 NA
Modified Hoehn & Yahr Stage,
a
mode (range) 2 (1–3) NA
UPDRS, handling utensil,
b
mode (range) 1 (0–3) NA
UPDRS, resting tremor,
b
mode (range) 1 (0–3) NA
UPDRS, postural tremor,
b
mode (range) 1 (0–3) NA
UPDRS, rigidity,
b
mode (range) 1 (0–3) NA
UPDRS, bradykinesia,
c
mode (range) 1 (0–5) NA
PD, Parkinson’s disease; UPDRS, Unified Parkinson’s Disease Rating Scale.
25
a
The Modified Hoehn and Yahr scale
24
(range 1–5) is used to evaluate the severity of PD: 1 means
mild and 5 means severe.
b
The measure was taken on the dominant upper limb only and the score can range from 0 (normal)
to 4 (severe) for each test.
c
The scores of bradykinesia were the sum of three subtests in the UPDRS: finger taps, hand
movements, and rapid alternating movements of the dominant hand. The score of each subtest
can range from 0 (normal) to 4 (severe).
Effect of utensil weight in Parkinson’s disease 1089
The participants moved with higher peak velocity,
fewer movement units and shorter acceleration
phase (in reach segment only) with a lightweight
spoon than with a weighted one. With respect to
the group difference, the participants with
Parkinson’s disease had lower peak velocity than
the controls.
While previous studies examining the effect of
weights focused primarily on measuring tremor
and found no significant effect of weights,
7–10
our study provides unique evidence that weight
affects movement kinematics during a functional
upper-extremity task in people with Parkinson’s
disease. In addition, contrary to the traditional
belief about the advantages of weighted utensils,
our results demonstrate the benefits of using light-
weight or normal-weight utensils.
Our results show higher peak velocity and lower
percentage of movement time for acceleration
phase in the lightweight condition than in the
weighted condition. A lightweight utensil requires
less force to grasp and is easier to move (less resis-
tant). Therefore, the participants’ movement can
be quickly accelerated to a high peak velocity.
The participants generated higher velocity
movements more quickly with the lightweight
utensil than with the heavier ones.
In our study, the Parkinson’s disease group had
significantly lower peak velocity and slightly
longer acceleration phase than the control group.
Although we did not measure the force of the
digits directly, the kinematic variable of peak
velocity reflects the force associated with arm
movement. Previous studies
11–13
have reported
impaired control of grasping force and late imple-
mentation of appropriate force amplitude among
the digits during object lift in Parkinson’s disease.
Our findings suggest that, compared with the con-
trols, the participants with Parkinson’s disease had
less forceful movement and took slightly longer to
accumulate the impulse for movement. Overall,
our findings, along with those in the previous
reports,
11–13
suggest that people with Parkinson’s
disease have impaired force control not only in
grasping but also in arm movement.
Although we found no significant difference in
maximum grip strength between the Parkinson’s
disease and control groups, this might have been
due to the nature of the measurement and the sim-
plicity of the task. That is, the dynamometer
Table 2 Descriptive statistics and results of inferential statistics for each condition in people with Parkinson’s disease (PD)
and age-matched controls
Dependent variable Condition (spoon weight) Condition effect Group effect
Group Lightweight Control Weighted P-value Effect size rP-value
MT
reach&return
(s)
PD 2.69 0.41 2.68 0.48 2.72 0.41 0.118 0.27 0.880
Controls 2.65 0.33 2.69 0.38 2.72 0.38
PV
reach
(mm/s)
PD 353.04 68.01 347.93 68.21 348.64 63.58 0.044 0.34 0.004
Controls 431.15 79.38 430.21 77.00 413.73 72.10
PV
return
(mm/s)
PD 239.94 35.20 237.39 40.00 232.82 34.67 0.013 0.41 0.021
Controls 281.24 62.15 271.89 60.32 272.59 64.37
PTA
reach
(%)
PD 37.44 8.63 37.63 9.05 38.35 9.59 0.010 0.43 0.139
Controls 32.51 6.50 32.19 6.52 34.81 7.95
PTA
return
(%)
PD 60.25 8.31 60.39 10.12 61.26 7.38 0.355 0.16 0.454
Controls 58.48 7.38 59.05 9.26 58.96 8.55
NMU
reach&return
PD 22.18 4.55 22.07 4.69 22.68 4.31 0.045 0.34 0.262
Controls 19.89 5.54 20.85 4.41 21.36 5.06
Values are means SD; MT, movement time; PV, peak velocity; PTA, percentage of movement time for acceleration phase;
NMU, number of movement units.
1090 Hui-Ing Ma et al.
recorded only the final outcome of the maximum
force, while the kinematic analysis delineated the
process of carrying out a movement. In addition,
using the dynamometer required the participant to
hold the apparatus in a static position and exert
maximum grip strength, while our experimental
task required the participant to coordinate finger-
tip forces with the movement of the proximal com-
ponent (i.e. arm movement). Because people with
Parkinson’s disease have difficulty temporally
coordinating multiple effectors during move-
ment,
11,26
our experimental task appears to have
been more challenging to them than the grip-
strength test. Therefore, we found a deficit of
force control in the kinematic analysis of our
experimental task, but not in the measurement of
the dynamometer. Our findings also suggest the
importance of choosing appropriate tasks and
measurement methods to understand the motor
control deficits in Parkinson’s disease.
There were limitations in this study. First, we
provided utensils weighted 35 g, 85 g and 135 g.
Our heaviest spoon was still much lighter than
the merchandized weighted utensils, which weigh
up to 200 g (7–8 oz). Although we expect the effect
of weight to be more pronounced with heavier
utensils, it is important in future research to
include utensils with heavier weight (e.g. 200 g)
to test whether even heavier utensils significantly
affect movement time and whether the heavier
utensils adversely affect movement kinematics
more in the Parkinson’s disease group than in
the control group. In addition, most of our parti-
cipants with Parkinson’s disease had slight tremor,
rigidity and bradykinesia and reported some
clumsiness when using utensils. Future research
should recruit participants with more advanced
Parkinson’s disease to determine whether the ben-
efits of lightweight utensils are similar in that
population.
In conclusion, we showed that the weight of a
utensil influences the movement kinematics of a
functional food transfer task in people with
Parkinson’s disease. A lightweight utensil elicited
higher velocity and smoother movement than a
heavier utensil. Consequently, with a lightweight
utensil, people with Parkinson’s disease may feel
better in controlling the movement and more effi-
cient in doing the task, thus reducing the
frustration caused by bradykinesia, unsteady
movement and possible food spillage.
Our study provides important evidence for
therapists to consider when making clinical recom-
mendations for adapted utensils. If the treatment
goal is to facilitate high-velocity and smooth
movement, a lightweight utensil seems to be
more appropriate than a heavier one for people
with Parkinson’s disease.
Clinical messages
The weight of a utensil influences the move-
ment kinematics of performing a functional
food-transfer task in people with
Parkinson’s disease.
To facilitate high-velocity and smooth arm
movement for people with Parkinson’s dis-
ease, a lightweight utensil seems to be more
appropriate than a weighted one.
Acknowledgement
This project was supported, in part, by grant
NSC 92–2314-B-006-027 from the National
Science Council, Taiwan.
References
1 Carr JH, Shepherd RB. Neurological rehabilitation:
optimizing motor performance. London: Elsevier,
2004.
2 Gillen G. Maximizing independence: occupational
therapy intervention for patients with Parkinson’s
disease. In Cote L, Sprinzeles LL, Elliott R,
Kutscher AH. eds. Parkinson’s disease and quality
of life. New York: Haworth, 2000: 65–67.
3 Newell KM. Constraints on the development of
coordination. In Wade MC, Whiting HTA. eds.
Motor development in children: aspects of
coordination and control. Dordrecht: Martinus
Nijhoff, 1986: 341–60.
4 Newell KM, Valvano J. Therapeutic intervention
as a constraint in learning and relearning move-
ment skills. Scand J Occup Ther 1998; 5: 51–57.
Effect of utensil weight in Parkinson’s disease 1091
5 Pedretti LW, Early MB. Occupational therapy:
practice skills for physical dysfunction,
fifth edition. St. Louis, MO: Mosby, 2001.
6 Radomski MV, Trombly LCA. Occupational
therapy for physical dysfunction, sixth edition.
Baltimore: Lippincott Williams &
Wilkins, 2008.
7 Hewer RL, Cooper R, Morgan MH. An
investigation into the value of treating intention
tremor by weighting the affected limb. Brain 1972;
95: 579–90.
8 Morgan MH, Hewer RL, Cooper R. Application
of an objective method of assessing intention
tremor - a further study on the use of weights to
reduce intention tremor. J Neurol Neurosurg
Psychiatry 1975; 38: 259–64.
9 Homberg V, Hefter H, Reiners K, Freund HJ.
Differential effects of changes in mechanical
limb properties on physiological and pathologi-
cal tremor. J Neurol Neurosurg Psychiatry 1987;
50: 568–79.
10 Meshack RP, Norman KE. A randomized
controlled trial of the effects of weights on
amplitude and frequency of postural hand tremor
in people with Parkinson’s disease. Clin Rehabil
2002; 16: 481–92.
11 Muratori LM, McIsaac TL, Gordon AM,
Santello M. Impaired anticipatory control
of force sharing patterns during whole-hand
grasping in Parkinson’s disease. Exp Brain Res
2008; 185: 41–52.
12 Rearick MP, Stelmach GE, Leis B, Santello M.
Coordination and control of forces during
multifingered grasping in Parkinson’s disease.
Exp Neurol 2002; 177: 428–42.
13 Santello M, Muratori L, Gordon AM. Control of
multidigit grasping in Parkinson’s disease: effect
of object property predictability. Exp Neurol
2004; 187: 517–28.
14 Rosenthal R, Rosnow RL. Essentials of behavioral
research: methods and data analysis, third edition.
New York: McGraw-Hill, 2008.
15 Marquardt C, Mai N. A computational procedure
for movement analysis in handwriting. J Neurosci
Methods 1994; 52: 39–45.
16 Marquardt C. 3DAwin. V 1.0. 3-Dimensional
movement analysis. Munich: MedCom, 2000.
17 Wing AM, Lough S, Turton A, Fraser C,
Jenner JR. Recovery of elbow function in volun-
tary positioning of the hand following hemiplegia
due to stroke. J Neurol Neurosurg Psychiatry
1990; 53: 126–34.
18 Flowers K. Ballistic and corrective movements on
an aiming task: intention tremor and parkinso-
nian movement disorders compared. Neurology
1975; 25: 413–21.
19 Nelson WL. Physical principles for economies of
skilled movements. Biol Cybern 1983; 46: 135–47.
20 Georgopoulos AP. On reaching. Annu Rev
Neurosci 1986; 9: 147–70.
21 Brooks VB, Cooke JD, Thomas JS. The continu-
ity of movements. In Stein RB, Pearson KG,
Smith RS, Redford JB. eds. Control of posture
and locomotion. New York: Plenum Press, 1973:
257–72.
22 Rosenthal R, Rosnow RL, Rubin DB.
Contrasts and effect sizes in behavioral research: a
correlational approach. New York: Cambridge
University Press, 2000.
23 Cohen J. Statistical power analysis for the
behavioral sciences, second edition. Hillsdale, NJ:
Lawrence Erlbaum, 1988.
24 Hoehn MM, Yahr MD. Parkinsonism: onset,
progression and mortality. Neurology 1967; 17:
427–42.
25 Fahn S, Elton R. The unified Parkinson’s disease
rating scale. In Fahn S, Marsden C, Calne D,
Goldstein M. eds. Recent developments in
Parkinson’s disease. New York: Macmillan, 1987:
153–304.
26 Bertram CP, Lemay M, Stelmach GE. The effect
of Parkinson’s disease on the control of multi-seg-
mental coordination. Brain Cogn 2005; 57: 16–20.
1092 Hui-Ing Ma et al.
